1. Field of the Invention
The present invention relates to a process of manufacturing a semiconductor device. In particular, the present invention relates to a method of forming a resist pattern for forming a micropattern on a wafer surface.
2. Description of the Related Art
In general, a process of manufacturing a semiconductor device includes many patterning processes. Specifically, according to the process of manufacturing a semiconductor device, various material layers are formed on a silicon wafer, and then, a desired pattern is formed on the silicon wafer and the material layer. In this case, a photosensitive substance called a resist is coated on a film to be processed. Then, a predetermined area of this resist film is exposed. An exposed or non-exposed portion of the resist film is removed by development to form a resist pattern. Thereafter, the film is dry-etched using the resist pattern as an etching mask.
In view of throughput, ultraviolet rays such as a KrF excimer laser and ArF excimer are used as a light source for exposing the resist film. However, advances in LSI scale reduction have been made, and therefore, the wavelength of a required resolution is shorter than that of these ultraviolet rays. For this reason, an exposure process margin such as exposure margin and focusing margin is short.
In order to solve the problem, an immersion exposure technique (e.g., see Jpn. Pat. Appln. KOKAI Publication No. 2006-119292) has been proposed and employed as a technique of improving resolution using a conventional exposure light. However, the technique has, as of today, the following problem. Specifically, an immersion liquid comes into the rear of a wafer in exposure, and thereby, there is a problem that focusing accuracy is reduced. If the immersion comes into the rear of the wafer to contact with a stage, the temperature of the immersion liquid is reduced. This temperature change of the immersion liquid is a factor of causing misalignment of a focusing position. For this reason, it is desired to solve the problem that the immersion liquid comes into the rear of the wafer.